Painless blood-collecting method

ABSTRACT

A method for collecting small amounts of blood sample by painless puncture of a finger. When puncture of skin of a human being by a needle or another device is performed at the depth of no more than 0.5 mm, pain accompanied by the puncture is diminished or decreased. Regardless of an error in the depth of the puncture, the depth of puncture always needs to not exceed this depth. The site of puncture is the dorsal surface of a finger, that is, the area from finger joint (IP joint of thumb, DIP joint of fingers other than thumb) to proximal nail wall and the area extending from proximal nail wall to lateral nail wall.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for collecting small amount of blood sample by painless puncture of hand fingers.

2. Prior Art

Self monitoring of blood glucose (SMBG) of diabetic patients has been performed by using blood obtained by needle puncture of finger tips (palm side, lateral side) containing many pain spots. As to the depth of puncture achieved by puncture device used for SMBG, preferably it may be in the range of 0.5 mm to 2.0 mm. Moreover, the range of 0.7 mm to 1.3 mm has been considered to be important particularly (refer to U.S. Pat. No. 5,318,584). Moreover, the error in the depth of puncture has been known to be more than ±0.3 mm (refer to U.S. Pat. No. 5,318,584). According to the conventional technique, pain accompanied with puncture of finger tips can not be avoided, for the puncture is performed at the site with many pain spots and the depth of the puncture is deep. Recently, by performing puncture at abdominal or forearm having comparative scarce pain spots, attempts to avoid pain accompanied with blood collection have been under way. However, complete elimination of pain can not be realized by using this method. Moreover, delayed alteration in blood glucose level measured by puncture of forearm compared with fingertip has been reported. Therefore, there has been demand on development of a painless blood collection method from fingers.

SUMMARY OF THE INVENTION

This invention relates to a method for collecting blood with decreased pain, by performing puncture of fingers at the site having little pain spots with shallow depth.

The area of puncture: At present, when collecting blood from finger tips, puncture of dorsal surface of a finger has not been guided to patients, despite of having less pain spots. According to present invention, the area of a finger approximate to the nail root is adopted for the site of blood collection, for the area has abundant blood-stream and thus bleeding is easy. According to this invention, the area of puncture in the dorsal surface of a finger is the area from finger joint (IP joint of thumb, DIP joint of fingers other than thumb) to proximal nail wall and the area extending from proximal nail wall to lateral nail wall (FIG. 1: 2). The most preferred area for puncture is the area of proximal nail wall and the area extending from proximal nail wall to lateral nail wall (FIG. 1: 2 a).

The depth of puncture: The thickness of skin epidermis of a body, except for palma manus and planta pedis, is from 0.07 mm to 0.12 mm. The skin epidermis of palma manus and that of planta pedis are more thick, reaching to 0.8 mm for palma manus and 1.4 mm for planta pedis. Then dermis underlies downside of the epidermis. Just under the dermis, there are blood vessels such as dermal papillary loops and subpapillary plexus. Free nerve ending involved in pain sensation entries from the epidermis to the dermis. Therefore, for the purpose to achieve skin puncture with decreased pain, the depth of puncture needs to be set at the minimal depth that can injure blood vessel existing just downside of the dermis. If the depth of the puncture is shallow, the damage brought to the skin tissue decreases. Considering matters described above, skin puncture was performed to the fingers of volunteers at the depths of 0.2, 0.3, 0.4, 0.5 and 0.6 mm (as described below). As the result, the depth of puncture that enables painless puncture is set as follows. The depth of puncture is no more than 0.5 mm. Even if some error occurs on the depth of puncture, it is necessary that the depth of puncture does not always exceed this range.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 shows the site of puncture in the dorsal surface of a finger. The explanation of the numerals in the drawing is described below.

(1) nail, (2) site of puncture, (2 a) the most preferred site for puncture, (3) finger joint (IP joint of thumb, DIP joint of fingers other than thumb).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The method to obtain blood sample from the site of puncture: In many cases, sufficient amount of blood can not be obtained only by puncture of skin, for the depth of puncture is shallow according to this invention. Then, after performing puncture to a finger, congestion at the site of puncture may be achieved, for example by inflecting finger joint (IP joint of thumb, DIP joint of fingers other than thumb) of the punctured finger, by making compression or avascularization at a proximal area from the puncture site on the finger, or by compressing finger tip of the punctured finger, thereby bleeding is enhanced.

EXAMPLE

To determine the depth of puncture that enables painless puncture, puncture was performed at the puncture site described above using various depths of puncture. A puncture device provided by TERUMO (Medisafe Fine Touch) was converted for shallow puncture. Using this device, skin puncture was performed at the depths of 0.2, 0.3, 0.4, 0.5 and 0.6 mm. Error on the puncture depth was ±0.13 mm at the maximum. Blood glucose was measured using the blood obtained by the skin puncture. A device for SMBG provided by TERMO (Medisafe Voice) was used for determination of blood glucose. According to this device, 2 μl of blood sample is needed for measurement of blood glucose.

Thirty-five healthy volunteers joined to this investigation. For each of five fingers randomly selected for each volunteer, depths of puncture i.e. 0.2, 0.3, 0.4, 0.5 and 0.6 mm were assigned randomly. When depth of puncture was 0.2 mm, twice punctures were needed for measurement of blood glucose at two volunteers. As to other volunteers, blood glucose was measurement at once puncture. Among the thirty-five volunteers, 31 volunteers (89%) with puncture depth of 0.2 mm, 33 volunteers (94%) with puncture depth of 0.3 mm, 23 volunteers (66%) with puncture depth of 0.4 mm, 16 volunteers (46%) with puncture depth of 0.5 mm, and 6 volunteers (17%) with puncture depth of 0.6 mm, did not feel any pain. Compared with puncture depth of 0.2 mm, the ration of individuals who felt no pain decreased with significance in the case the puncture depth was more than 0.4 mm. As the result of this investigation, to achieve puncture of fingers without pain, it is necessary to achieve puncture at the depth of no more than 0.5 mm including error.

INDUSTRIAL APPLICABILITY

The painless method for collecting blood according to this invention is not only useful to decrease pain of the subject at collecting blood, the method is also advantageous on medical economics. When a portion of body except for finger is punctured for blood collection, aspiration of blood using vacuum pump from the site of puncture may be needed to obtain the blood sample. However, in the method of collecting blood according to this invention, a device such as vacuum pump is not needed. Moreover, to perform SMBG, a conventional and wide-spread device for measurement of blood glucose may be utilized as it is. Therefore, this invention provides a painless system for blood glucose measurement to many diabetic patients at low cost. 

1. A method for collecting blood with little pain satisfying both of following two criteria, comprising puncture of a finger of a human being by a needle or another device, wherein: (a) the depth of skin puncture is no more than 0.5 mm, (b) the site of puncture to be used in the dorsal surface of a finger is the area from finger joint (IP joint of thumb, DIP joint of fingers other than thumb) to proximal nail wall and the area extending from proximal nail wall to lateral nail wall (2), the most preferred area for puncture is the area of proximal nail wall and the area extending from proximal nail wall to lateral nail wall (2 a).
 2. The method according to claim 1, the method further comprising the step of enhancing of bleeding, by inflecting finger joint (IP joint of thumb, DIP joint of fingers other than thumb) (3) of the punctured finger, by making compression or avascularization at a proximal area from the puncture site on the finger, or by compressing finger tip of the punctured finger. 